President Barack Obama attends a campaign rally for Maryland Gov. Martin O'Malley, second from right Thursday at Bowie State University in Bowie, Md. At right is Sen. Barbara Mikulski, D-Md. At left is Maryland Lt. Gov. Anthony Brown.

With little more than three weeks until the midterm elections, Democrats and Republicans are in a ferocious fight over the most important issue in the campaign: money.

Not taxes or deficits or bailouts, but the cash pouring in to both parties and being doled out to candidates around the country.

So far, the GOP has a considerable edge. It’s corporate and conservative interest group benefactors are writing checks like there’s no tomorrow, allowing the party to fund campaign ads in many more races than might otherwise have been the case – including those once thought safe for Democrats.

Analyzing reported spending, the Washington Post finds that Republicans have spent at least $100,000 in 77 different congressional races (nearly twice the number of seats they need to gain control of the House), compared with 43 races in which Democrats have spent that much.

Looked at across regions of the country, Republicans and their supporters are outspending their Democratic counterparts by 53 percent, the newspaper reports: $74.6 million to $39.7 million, based on Federal Election Commission filings. At the same time, millionaire and billionaire candidates – Republicans Meg Whitman, Carly Fiorina, and Linda McMahon among them – are digging into their personal pocketbooks to battle their opponents on the airwaves.